In comparison to the second or third generation mobile communication system, e.g. GSM/UMTS (Global System for Mobile Communication/Universal Mobile Telecommunication System) systems, the fourth generation mobile communication system, e.g. LTE (Long Term Evolution) system, could achieve higher wireless uploading and downloading data rates, and could provide the users with better mobile broadband Internet and wireless multi-media service.
In order to reduce the opportunity of users having to change mobile phones for different mobile communication systems used in different countries or areas, the mobile communication devices of LTE system must also be capable of GSM/UMTS operations. Thus, a compact antenna whose operating bands could meet the bandwidth requirements of LTE, GSM, and UMTS systems for multiband and wideband operation has become an important study topic.
For designing a single antenna to meet the bandwidth requirement of dual-band operation for GSM850/GSM900 systems (824˜960 MHz), operating bandwidth of the antenna around 890 MHz must be larger than 136 MHz (the fractional bandwidth is about 16%). However, for designing a single antenna to meet the bandwidth requirement of tri-band operation for LTE700/GSM850/GSM900 systems (698˜960 MHz), operating bandwidth of the antenna around 830 MHz must be larger than 260 MHz (the fractional bandwidth is about 30%), wherein the required operating bandwidth is nearly doubled. Besides, it is even more difficult for the case of designing the single antenna capable of LTE700/GSM850/GSM900 operation to further meet the bandwidth requirement of penta-band operation for GSM1800/GSM1900/UMTS/LTE2300/LTE2500 systems (1710˜2690 MHz) at higher frequency bands simultaneously, that is, operating bandwidth of the antenna around 2200 MHz must also be larger than 460 MHz (the fractional bandwidth is larger than 40%).
Thus, it is indeed a challenge of designing a single antenna to meet bandwidth requirements of the tri-band operation for LTE700/GSM850/GSM900 systems and the penta-band operation for GSM1800/GSM1900/UMTS/LTE2300/LTE2500 systems in a limited space of a mobile communication device.